The invention relates to an axial bearing comprising two parts which are rotatable relative to each other about an axis of rotation, comprising a first surface and a second surface facing the first surface, said first surface being provided with at least a pattern of bearing grooves, which pattern, as the surfaces rotate relative to each other, acts to build up a pressure in a viscous medium present in a gap formed between the two surfaces during operation.
Such an axial bearing is known from Netherlands Patent Application 7,213,192 to which U.S. Pat. No. 3,870,382 coresponds, herewith incorporated by reference. In the known bearing two patterns of bearing grooves are formed, which patterns produce opposed pressures in the viscous medium between the bearing surfaces during a rotary movement of one part relative to the other part, which medium may be a liquid lubricant such as oil or grease. For a correct operation of the bearing it is necessary that under operating conditions there is always an adequate amount of lubricant between the surfaces, in particular at a location of the bearing grooves. Since in practice there is always some loss of viscous medium, for example as a result of leakage and evaporation, the known bearing will have lost such an amount of viscous medium after some time that it is no longer possible to build up an adequate pressure, which renders the bearing unreliable and hence not suitable for further use.